Cocoon Nebula: Floating on a silted stream

[Howard]

Hello: I shot the raw frames for this image of the Cocoon nebula in summer of 2013, 10+ hours of LRGB, but it's taken me until now to complete the image processing (somehow, with each new image, it takes me longer to work through the processing workflow, but this time was ridiculous !). I hope this framing of the emission nebula may fancifully suggest a fall-coloured leaf floating on a silted stream, with the stars crowding the corners giving the impression of multicoloured gems deposited there by the current . I downsampled this JPG for the upload, here's the full res version. I struggled mightily to bring out the faint dusty nebula without blowing out the rest of the image or generating too much noise in the weak signal regions. I also found the very busy star field to be tough to manage, though I used the standard technique of applying the MorphologicalTransformation tool to shrink the stars, hopefully without changing the relative balance between brighter and dimmer stars too much. I also found the colour balance to be tricky, given the wide range of image structures. Choices, choices, choices … the boon/bane of image processing . Anyway, thanks for looking!

[Dimitris Platis]

That is fantastic processing!
WOuld u mind sharing ur workflow or even perhaps some hints about how u managed to bring out this nebula so clearly?

Dimitris

[Howard]

Hi Dimitris:

Thank you for your very kind words!

To try to bring out the structures on multiple scales I use a combination of the HDRMultiscaleTransform (HDR), MultiscaleMedianTransform (MMT), and LocalHistogramEqualization (LHE) tools. In the PixInsight tutorials it seems that HDR with LHE does the job, but I find I usually need to add the MMT as an intermediate step to fully expose the multiscale structures. I don't know why HDR/LHE isn't enough for me, and I do spend an awful lot of time experimenting with the parameters in each tool (as with all the tools in the workflow!) to find the best combination I can. Hope that helps, but look to the PixInsight tutorials for authoritative examples and workflows .

Cheers,
Howard.

[RickS]

Very nice, Howard!

[Howard]

Hi Rick:

Thanks so much!

I took a peak at some of your images, the Helix in particular stopped me in my tracks, one of the best I've seen, amazing depth and resolution!

Howard.

[jkmorse]

Howard,

Hell of an image!!  Have to say I love the star field and the rish, deep colors, as much as I like the nebula.  Beautiful.

Best,

Jim

[Howard]

Hi Jim:

Thanks so much for your very kind feedback!

Howard.
P.S. I downloaded your very thorough crib sheet today and found some very useful suggestions that I'm going to try out on my next image .

[jkmorse]

Great.  I have updated quite a bit depending on which version you downloaded.  I am up to Rev27 now so if you would like the latest, just drop me a line at jkmorse57@gmail.com.

Best,

Jim

[topboxman]

Howard,

I think your Cocoon looks great. Great colors.

It looks like the background might be clipped a tad too much. It's probably because the file might be severely compressed for uploading to this site.

Peter

[Howard]

Hi Peter:

Thanks for taking the time for a closer look at the image. Yes, the version I uploaded is downsampled by 2, and the compression chopped the black point alot. The original JPG has a decent blackpoint (that JPG is available here), though even in that case the compression chopped the blackpoint somewhat compared to the FITS (the FITS is here, for what it's worth, but ~49MB!). I didn't realize that the blackpoint can take such a hit with compression - I just tried various ICCProfileTransformation settings to see if the JPG blackpoint can be improved, but they all seemed to turn out about the same, do you have any suggestions? Happily, in practice, the JPG looks quite close to the FITS, at least in my display .

Cheers,
Howard.